The present invention relates to an ethylene-xcex1-olefin copolymer obtained by a gas phase polymerization method in the presence a catalyst, a polyethylene composition comprising said copolymer, and a film made of said copolymer or composition. More particularly, the present invention relates to an ethylene-xcex1-olefin copolymer which contains a small amount of a cold xylene-soluble portion (CXS component) and does not easily cause problems such as blocking and the like when made into a film or sheet, a polyethylene composition which is excellent in appearances such as gloss, transparency and the like when made into a film and is excellent in handling properties such as blocking-resistance, slipping property and the like, and a film composed of said copolymer or said composition.
Properties required for films used as wrapping materials include excellent film-forming processability in processing a film, excellent appearances such as the gloss, transparency and the like concerning clear visibility of contents, easy handling in bag manufacturing, and excellent blocking-resistance, slipping property and the like of a film concerning easiness in opening a bag in filling, particularly, in automatic filling, and the like.
As the ethylene-based resin used for such films, ethylene-xcex1-olefin copolymers are listed.
An ethylene-xcex1-olefin copolymer obtained according to a high-pressure ion polymerization method in the presence of a catalyst had problems such as fuming in molding working, inclusion of a volatile component which is a cause for generation of a gas, and the like, due to problematical process (Japanese Patent Application Laid-Open (JP-A) No. 52-125590).
On the other hand, a copolymer produced by a gas phase polymerization method has a merit that the content of a volatile component causing gas generation and fuming in molding working is low, as the polymerization can be performed substantially in the absence of a solvent.
The ethylene-xcex1-olefin copolymer obtained by a gas phase polymerization method also had problems that the copolymer contains a large amount of a cold xylene-soluble portion (CXS component) causing blocking and the like (JP-A No. 54-154488), or the copolymer has a little hexane extracted portion, however, the content of a cold xylene-soluble portion (CXS component) becomes high (JP-A No. 5-155938).
JP-A No. 56-152853 discloses a resin composition comprising an ethylene-xcex1-olefin copolymer obtained by a gas phase polymerization method in the presence a catalyst and a low density polyethylene produced by a high pressure radical polymerization method, and a film thereof. However, a film obtained from said composition has not been satisfactory in transparency and gloss, though the impact strength thereof has been improved. Further, JP-A No. 56-152853 does not disclose the addition of an anti-blocking agent and slipping agent, therefore anti-blocking property and slipping property have not been satisfactory.
Therefore, there has been desired for an ethylene-xcex1-olefin copolymer or resin composition which has lower content of a volatile component, causes no problems such as gas generation, fuming and the like in molding working, has a small amount of a cold xylene-soluble portion (CXS component), does not easily cause problems such as blocking and the like when made into a film or sheet, and has good balance between appearances of a film such as gloss, transparency and the like and handling properties thereof such as anti-blocking property, slipping property and the like.
The present inventors have intensively studied a copolymer and a composition containing the composition which have no problems as described above, and resultantly found that a specific ethylene-xcex1-olefin copolymer obtained by a gas phase polymerization method has a small amount of a cold xylene-soluble portion (CXS component) and does not easily cause problems such as blocking and the like when made into a film or sheet. Further, the present inventors have found that a resin composition comprising said and a specific low density polyethylene obtained by a high pressure radical polymerization method, when made into a film, has a small content of a volatile component, provides no problems such as fuming, gas generation and the like in molding, has excellent appearances such as gloss, transparency and the like, and has excellent handling properties such as anti-blocking property, slipping property and the like, and have completed the present invention.
Namely, the present invention relates to a polyethylene composition comprising 60 to 95 wt % of an ethylene-xcex1-olefin copolymer component (A) obtained by a gas phase polymerization method in the presence of a catalyst and 5 to 40 wt % of a low density polyethylene component (B) obtained by a high pressure radical polymerization method (wherein, the total amount of component (A) and component (B) is 100 wt %), wherein said ethylene-xcex1-olefin copolymer component (A) satisfies the following conditions (A-1) to (A-4):
(A-1) Melt flow rate (MFR): 0.3 to 5.0 g/10 minutes
(A-2) Melt flow rate ratio (MFRR): 20 or more
(A-3) Density (d): 0.910 to 0.930 g/cm3 
(A-4) Cold xylene-soluble portion (CXS) (wt %) is in the range defined by the formula (1):
1.5xc3x9710xe2x88x924xc3x97dxe2x88x92125xc3x97MFR0.5+0.3xe2x89xa7CXSxe2x80x83xe2x80x83formula (1).
The present invention will be illustrated in detail below.
The gas phase polymerization method of the present invention is not particularly restricted providing it is a method in which no solvent substantially exist, and polymerization is performed under solid phase or gas phase to produce a polymer. Known reactors such as a vertical reactor, horizontal reactor and the like can be used. Reactors may or may not have a stirrer. Further, a plurality of reactors may also be used. The production method may be continuous or batch-wise. The polymerization pressure is preferably from atmospheric pressure to 40 kg/m2, and the polymerization temperature is preferably from 55 to 95xc2x0 C.
The catalyst used in the present invention is a solid catalyst for olefin polymerization which can copolymerize ethylene with an xcex1-olefin. As the catalyst, there are listed, for example, catalyst systems described in Japanese Patent Application Nos. 10-59846, 10-59848, 11-65433 and the like.
The solid catalyst component (I) for olefin polymerization used in the present invention is a solid catalyst component for olefin polymerization obtained by contacting a halide of a XIII or XIV group element and an electron donor with a solid catalyst component precursor containing a magnesium atom, titanium atom and a hydrocarbyloxy group.
The halogen contained in the solid catalyst component (I) is a halogen atom in the XVII group of the periodic table, for example, chlorine atom, bromine atom, iodine atom or the like, and preferably chlorine atom.
The electron donor contained in the solid catalyst component (I) is an organic compound containing at least one atom selected from the group consisting of an oxygen atom, sulfur atom, nitrogen atom and phosphorus atom, and for example, amines, sulfoxides, ethers, esters or the like are listed, and ethers and esters are preferable.
As the ethers, dialkyl ethers are listed, and specifically, diethyl ether, dibutyl ether, tetrahydrofuran and the like are listed. Dibutyl ether and tetrahydrofuran are preferable.
Examples of the esters include saturated aliphatic carboxylates, unsaturated aliphatic carboxylates, alicyclic carboxylates, aromatic carboxylates and the like. Specifically, there are listed ethyl acetate, ethyl acrylate, ethyl methacrylate, butyl benzoate, dibutyl succinate, dibutyl malonate, dibutyl maleate, dibutyl itaconate, di-n-butyl phthalate, diisobutyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate and the like, and di-2-ethylhexyl phthalate and di-n-octyl phthalate are preferable.
The solid catalyst component (I) can be obtained by cotacting a halide of a XIV group element and an electron donor with a solid catalyst component precursor containing magnesium, titanium and a hydrocarbyloxy group, and further contacting with a compound having a Ti-halogen bond.
As the solid catalyst component precursor containing magnesium, titanium and a hydrocarbyloxy group, a solid product containing a tri-valent titanium atom is preferable which is obtained by reducing a titanium compound represented by the general formula Ti(OR1)aX4xe2x88x92a (wherein, R1 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, and a represents a number satisfying 0 less than axe2x89xa64) with organo-magnesium, in the presence of an organo-silicon compound having a Sixe2x80x94O bond.
As the organo-silicon compound having a Sixe2x80x94O bond, tetramethoxy silane, tetraethoxy silane, tetrapropoxy silane, tetrabutoxy silane and the like are listed, and tetrabutoxy silane is preferable.
As the hydrocarbon group (R1) of the titanium compound represented by the general formula Ti(OR1)aX4xe2x88x92a (wherein, R1 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, and a represents a number satisfying 0 less than axe2x89xa64), there are listed, for example, a methyl group, ethyl group, propyl group, butyl group and the like, and a butyl group is preferable.
As the halogen atom (X) of the titanium compound represented by the general formula Ti(OR1)aX4xe2x88x92a, there are listed a chlorine atom, bromine atom, iodine atom and the like, and a chlorine atom is preferable. a is 1, 2, 3 or 4, and is preferably 4.
Examples of the titanium compound represented by the general formula Ti(OR1)aX4xe2x88x92a include butoxytrichlorotitanium, dibutoxydichlorotitanium, tributoxychlorotitanium, tetrabutoxytitanium and the like, and tetrabutoxytitanium is preferable.
As the organo-magnesium, Grignard""s compounds having a Mg-carbon bond, and the like are listed. Examples thereof include methylchloromagnesium, ethylchloromagnesium, propylchloromagnesium, butylchloromagnesium and the like, and butylchloromagnesium is preferable.
As the halogen compound in XIV group to be contacted with a solid catalyst precursor, halides of a carbon atom and silicon atom are listed, and halides of a silicon atom represented by the general formula SiR24xe2x88x92bXb (wherein, R2 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, and b represents a number satisfying 0 less than bxe2x89xa64) are preferable.
As the hydrocarbon group (R2) of the silicon compound represented by the general formula SiR24xe2x88x92bXb (wherein, R2 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, and b represents a number satisfying 0 less than bxe2x89xa64), there are listed, for example, a methyl group, ethyl group, propyl group, butyl group and the like, and a butyl group is preferable.
As the halogen atom (X) of the silicon compound represented by the general formula SiR24xe2x88x92bXb, there are listed a chlorine atom, bromine atom, iodine atom and the like, and a chlorine atom is preferable. b is 1, 2, 3 or 4, and is preferably 3 or 4.
Examples of the silicon compound represented by the general formula SiR24xe2x88x92bXb include butyltrichlorosilane, dibutyldichlorosilane, trichlorobutylsilane, tetrachlorosilane and the like, and tetrachlorosilane is preferable.
As the electron donor to be contacted with a solid catalyst precursor, those described above are listed.
As the halogen of a compound having a Ti-halogen bond to be further contacted with a product obtained by contacting a halogen compound of a XIV group element and an electron donor with a solid catalyst component precursor, a chlorine atom, bromine atom, iodine atom and the like are listed, and a chlorine atom is preferable.
Examples of the compound having a Ti-halogen atom include tetrahclorotitanium, trichlorobutoxytitanium, dichlorodibutoxytitanium, chlorotributoxytitanium and the like, and tetrachlorotitanium is preferable.
The ethylene-xcex1-olefin copolymer of the present invention is an ethylene-xcex1-olefin copolymer produced on a solid catalyst component (I) obtained by contacting the solid catalyst component (I), organo-aluminum (II) and ethylene and xcex1-olefin.
In a gas phase polymerization method containing substantially no solvent, a process of recovering and purifying a solvent can be omitted, and the content of a volatile component causing gas generation and fuming in processing a film using the resulted ethylene-xcex1-olefin copolymer can be decreased.
The ethylene-xcex1-olefin copolymer (component (A)) of the present invention is a copolymer of ethylene with one or more xcex1-olefins having 3 to 12 carbon atoms.
Examples of the xcex1-olefin include propylene, butene-1, pentene-1,4-methyl-1-pentene, hexene-1, octene-1, decene-1 and the like. and propylene, butene-1, hexene-1 and octene-1 are preferable, and butene-1 and hexene-1 are further preferable.
Examples of the ethylene-xcex1-olefin copolymer (component (A)) are an ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer and the like, and an ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer and ethylene-octene-1 copolymer are preferable, and an ethylene-butene-1 copolymer and ethylene-hexene-1 copolymer are further preferable.
The content of the xcex1-olefin in the ethylene-xcex1-olefin copolymer (component (A)) is preferably from 0.5 to 30 mol %, particularly preferably from 1.0 to 20 mol %.
The melt flow rate (MFR) of the ethylene-xcex1-olefin copolymer (component (A)) is from 0.3 to 5.0 g/10 minutes, preferably from 0.5 to 3.0 g/10 minutes, particularly preferably from 0.7 to 2.5 g/10 minutes.
When the melt flow rate (MFR) is less than 0.3 g/10 minutes, problems easily occur such as excess extrusion load in film-forming, leading to occurrence of melt fracture, and the like. When the melt flow rate (MFR) is over 5.0 g/10 minutes, the mechanical property of a film deteriorates, and film-forming stability becomes insufficient.
The melt flow rate ratio (MFRR) of the ethylene-xcex1-olefin copolymer (component (A)) is 20 or more, preferably 21 or more.
When the melt flow rate ratio (MFRR) is less than 20, problems easily occur such as excess extrusion load in film-forming, leading to occurrence of melt fracture, and the like.
The density of the ethylene-xcex1-olefin copolymer (component (A)) is from 0.910 to 0.930 g/cm3, preferably from 0.915 to 0.930 g/cm3, particularly preferably from 0.918 to 0.927 g/cm3.
When the density is less than 0.910 g/cm3, deterioration in anti-blocking property, lack in rigidity and the like occur, decreasing the handling property of a film. When the density is over 0.930 g/cm3, the gloss and transparency of a film become insufficient.
The cold xylene-soluble portion (CXS)(wt %) in the ethylene-xcex1-olefin copolymer component (A) is in the range defined by the formula (1):
1.5xc3x9710xe2x88x924xc3x97dxe2x88x92125xc3x97MFR0.5+0.32xe2x89xa7CXSxe2x80x83xe2x80x83formula (1)
preferably, defined by the formula (2):
1.5xc3x9710xe2x88x924xc3x97dxe2x88x92125xc3x97MFR0.5xe2x89xa7CXSxe2x80x83xe2x80x83formula (2).
When the content of the cold xylene-soluble portion (CXS) is over the upper limit of the above-described formula (1), the anti-blocking property and slipping property of a film become insufficient. The lower limit is 0 or more.
The HL110 of the ethylene-xcex1-olefin copolymer is preferably in the range defined in the formula (3):
xe2x88x9268858xc3x97d2+124830xc3x97dxe2x88x9256505xe2x89xa7HL110xe2x80x83xe2x80x83formula (3).
Wherein, d is 0.910 to 0.930 g/cm3, preferably from 0.915 to 0.930 g/cm3, particularly preferably from 0.918 to 0.927 g/cm3.
If HL110 is over the range defined by the formula (3), when the copolymer is applied for a film, the toughness, rigidity and anti-blocking property of the film may become poor.
The ratio of the fusion calorie at 110xc2x0 C. or lower to the total fusion calorie measured by a differential scanning calorimeter (DSC) indicates the rigidity of an ethylene-xcex1-olefin copolymer.
Lower this value is, higher the rigidity of an ethylene-xcex1-olefin copolymer becomes.
The composition distribution variation coefficient Cx of an ethylene-xcex1-olefin copolymer is preferably 0.85 or less, further preferably 0.83 or less.
If the composition distribution variation coefficient Cx is over 0.85, when the composition is applied for a film, the strength of the film may decrease, and the anti-blocking property and transparency of the film may become poor.
The composition distribution variation coefficient Cx is a scale of the composition distribution of an ethylene-xcex1-olefin copolymer, and calculated according to the following formula.
Cx="sgr"/SCBave
"sgr": Standard deviation
SCBave: Average of number of short chain branches per 1000 carbon atoms
Lower this value is, narrower the composition distribution is.
The low density polyethylene component (B) of the present invention may be a low density polyethylene obtained by a high pressure radical polymerization method, and preferably a low density polyethylene obtained by homo-polymerizing ethylene according to a high pressure radical polymerization method.
The high pressure radical polymerization method of the present invention is a method in which polymerization is initiated using a radical generating agent under high pressure and obtained a polymer. In general, ethylene and the like are polymerized to obtain a polymer under a polymerization pressure of 1400 to 3000 kg/m2 and a polymerization temperature of 200 to 300xc2x0 C. in the presence of a radical generating agent such as a peroxide and the like using a vessel type reactor or tubular type reactor. A polymer obtained using a tubular type reactor contains a lower amount of microgel, and when the polymer is applied for a film, appearance failures such as fish eye and the like do not occur easily, therefore, it is preferable to use a tubular type reactor from the standpoint of the object of the present invention. The melt flow rate can be controlled by using hydrogen or hydrocarbon such as methane, ethane or the like which is a molecular weight controlling agent. The swell ratio (SR) and density can be controlled by optionally selecting the polymerization pressure and polymerization temperature in the above-described ranges.
The melt flow rate (MFR) of the low density polyethylene component (B) is preferably from 0.1 to 10 g/10 minutes, more preferably from 0.3 to 8.0 g/10 minutes, and particularly preferably from 0.8 to 6.0 g/10 minutes.
The swell ratio (SR) of the low density polyethylene component (B) is preferably from 1.40 to 1.60, more preferably from 1.45 to 1.58, particularly preferably satisfies the relation of the following formula (4) in the above-mentioned range, and most preferably satisfies the relation of the following formula (5) in the above-mentioned range.
xe2x88x920.09(log MFR)2+0.23 log MFR+0.04xc3x9720/Bwt+1.35  less than SR less than xe2x88x920.09(log MFR)2+0.23 log MFR+0.04xc3x9720/Bwt+1.50xe2x80x83xe2x80x83Formula (4)
xe2x80x83xe2x88x920.09(log MFR)2+0.23 log MFR+0.04xc3x9720/Bwt+1.40 less than SR less than xe2x88x920.09(log MFR)2+0.23 log MFR+0.04xc3x9720/Bwt+1.48xe2x80x83xe2x80x83Formula (5)
The density of the low density polyethylene component (B) is preferably from 0.900 to 0.935 g/cm3, and particularly preferably 0.915 to 0.930 g/cm3.
The melt tension (MT) of the polyethylene composition of the present invention is preferably from 1.8 to 5.5 g, more preferably from 2.0 to 5.0 g.
Regarding the compounding amounts (compounding ratios) of an ethylene-xcex1-olefin copolymer (component (A)) obtained by a gas phase polymerization method and a low density polyethylene (component (B)) obtained by a high pressure radical polymerization method, the amount of the component (A) is from 60 to 95 wt % and the amount of the component (B) is from 40 to 5 wt %, and preferably, the amount of the component (A) is from 70 to 93 wt % and the amount of the component (B) is from 30 to 7 wt %. Wherein, the total amount of the component (A) and the component (B) is 100 wt %.
The anti-blocking agent component (C) in the present invention can prevent mutual adhesion and fusion of a resin, and can prevent the resin from forming a larger block, and is used together with a resin. Particularly, the anti-blocking agent component (C) can prevent the mutual adhesion and fusion of a resin in the form of a sheet or film, and can prevent the resin from forming a larger block.
The anti-blocking agent component (C) in the present invention is not particularly restricted, and there are exemplified inorganic anti-blocking agents and organic anti-blocking agents.
As the inorganic anti-blocking agent, synthetic anti-blocking agents and natural anti-blocking agents are listed. As the inorganic synthetic anti-blocking agent, there are listed, for example, synthetic silica, and a powder of crystalline or amorphous alumino-silicate, and the like, and a powder of crystalline or amorphous alumino-silicate is preferable. As the inorganic natural anti-blocking agent, there are listed, for example, those obtained by grinding and calcinating silicon dioxide, clay, talk, diatomaceous earth, feldspar, kaolin, zeolite, kaolinite, wollastonite, sericite and the like. Further, the surfaces of these materials may be treated with a surface treating agent such as a higher fatty acid such as stearic acid and the like, titanium coupling agent, silane coupling agent and the like.
As the organic anti-blocking agent, synthetic anti-blocking agents are listed, and examples thereof include powders of cross-linked acrylic resins, cross-linked polyethylene-based resin, cross-linked polystyrene-based resin, cross-linked silicone-based resin, polyamide-based resin, polyester-based resin and the like. A powder of a cross-linked methylpolymethacrylate is preferable. Also in the case of the organic anti-blocking agents, the surfaces thereof may be treated with a surface treating agent such as a higher fatty acid such as stearic acid and the like, titanium coupling agent, silane coupling agent and the like, as in the case of the inorganic anti-blocking agents.
As the anti-blocking agent (C), two or more of the above-described anti-blocking agents may also be used together.
The compounding amount (compounding ratio) of the anti-blocking agent component (C) in the polyethylene composition of the present invention is preferably from 0.05 to 0.60 wt %, more preferably from 0.05 to 0.40 wt %. When the compounding amount of the anti-blocking agent (C) is less than 0.05 wt %, the anti-blocking property of a film may be insufficient. While when the compounding amount of the anti-blocking agent (C) is over 0.60 wt %, the optical property of a film may deteriorate.
The anti-blocking agent component (C) preferably has an average particle size of 1 to 10 xcexcm and a circular degree coefficient of 0.600 or more, more preferably has an average particle size of 3 to 6 xcexcm and a circular degree coefficient of 0.630 or more, from the standpoints of the appearance and anti-blocking property of a film. Further, two or more components having different average particle sizes and different circular degree coefficients may be used together.
Regarding the circular degree coefficient of the present invention, an image observed by an optical microscope is photographed, the image is treated by an image analyzer, and the circular degree coefficient S is calculated according to the following formula.
S=4xcfx80xc3x97A/L2
(A: area of image, L: circumference length)
This circular degree coefficient approximates 1 when the image is near circle. In the case of the above-mentioned anti-blocking agent component (C), the circular degree coefficient S is preferably from 0.600 to 1.000. More preferably, it is from 0.630 to 1.000, further preferably, it is from 0.700 to 1.000.
The slipping agent (D) of the present invention is used together with a resin so that the resins mutually slip easily when they come into contact with each other, and particularly, is used together with a resin so that the resins in the form of a sheet or film slip easily each other and can be handled easily.
The slipping agent (D) is not particularly restricted, and there are listed known fatty amide compounds, specifically, saturated fatty amides, unsaturated fatty amides, saturated fatty bisamides, unsaturated fatty bisamides and the like.
Examples of the saturated fatty amide are palmitic amide, stearic amide, behenic amide and the like, and behenic amide is preferable. Examples of the unsaturated fatty amide are oleic amide, erucic amide and the like, and erucic amide is preferable. Examples of the saturated fatty bisamide are ethylene-bis-palmitic amide, ethylene-bis-stearic amide, hexamethylene-bis-stearic amide and the like, and ethylene-bis-stearic amide is preferable. Examples of the unsaturated fatty bisamide are ethylene-bis-oleic amide, hexamethylene-bis-oleic amide, N,Nxe2x80x2-dioleylsebacic amide and the like, and ethylene-bis-oleic amide is preferable.
Two or more of the above-described slipping agents (D) may be used together. When two or more of the slipping agents (D) are used, a mixed system of an unsaturated fatty amide with a saturated or unsaturated fatty bisamide is preferable.
The compounding amount (compounding ratio) of the slipping agent (D) in the polyethylene composition of the present invention is preferably from 0.05 to 0.35 wt %, more preferably from 0.05 to 0.30 wt %. When the compounding amount of the slipping agent (D) is less than 0.05 wt %, the anti-blocking property and slipping property of a film may be insufficient. While when the compounding amount of the slipping agent (D) is over 0.35 wt %, the optical property and the like of a film may deteriorate due to excess bleeding of the slipping agent.
The method for producing the polyethylene composition of the present invention is not particularly restricted, and any known method can be used, and the composition is obtained by uniformly melting and kneading components used in the present invention. For example, there are listed a method in which components are mixed by a tumbler blender, henschel mixer and the like, then, the mixture is further melted and kneaded by a single-screw extruder or multi-screw extruder to give a granule, a method in which components are melted and kneaded by a kneader, banbury mixer and the like, then, the mixture is granulated using an extruder, as well as other methods.
It is also possible that an anti-blocking agent component (C) and/or slipping agent component (D) is melted and mixed in high concentration with an ethylene-xcex1-olefin copolymer component (A) and/or low density polyethylene component (B) to give a master pellet, then, this master pellet is compounded in necessary amount with the ethylene-xcex1-olefin copolymer component (A) and/or low density polyethylene component (B) to obtain the polyethylene composition of the present invention.
In the polyethylene composition of the present invention, at least one or more of various resins may be compounded, if necessary, to an extent not deteriorating the object of the present invention. For example, a high density polyethylene can be used for improving rigidity, and further, a polyolefin-based resin such as a low density elastomer and the like can be used for improving impact strength.
In the polyethylene composition of the present invention, known additives such as a stabilizer, antistatic agent, processability improving agent and the like usually used may also be contained, if necessary, to an extent not deteriorating the object of the present invention.
As the stabilizer, a phenol-based stabilizer, phosphite-based stabilizer and the like are listed. Examples of the phenol-based stabilizer include 2,6-di-t-butyl-p-cresol (BHT), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (IRGANOX 1010), n-octadecyl-3-(4xe2x80x2-hydroxy-3,5xe2x80x2-di-t-butylphenyl)propionate (IRGANOX 1076) and the like. Examples of the phosphite-based stabilizer include bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)4,4xe2x80x2biphenylene diphosphonite and the like.
Examples of the antistatic agent include fatty acid glycerin ester having 8 to 22 carbon atoms, sorbitan ester, polyethylene glycol ester and the like. As the processability improving agent, there are listed fatty acid metal salts, for example, calcium stearate and the like.
A film made of the polyethylene composition of the present invention can be obtained by an tubular process such as an air-cooling tubular process, water-cooling tubular process and the like. The thickness of a film is usually from 5 to 200 xcexcm. A film having a thickness of 50 to 200 xcexcm is more preferable in balance between appearances such as gloss, transparency and the like and handling properties such as anti-blocking property, slipping property and the like.
Regarding the processing of a film, the polyethylene composition of the present invention may be singly subjected to processing alone to give a film, or the polyethylene composition of the present invention may be laminated with other thermoplastic resin composition and processed to obtain a film. In the case of lamination and processing of a film, it is preferable that lamination and processing is so conducted that a layer composed of the polyethylene composition of the present invention is placed on one side or both sides of the outermost layer.
As the lamination and processing method, there are listed, for example, a co-extrusion tubular process, dry lamination process, sandwich lamination process and the like.
The co-extrusion tubular process is a method in which the polyethylene composition of the present invention and other resin are co-extruded, and a co-extruded film having two or more layers can be obtained. Examples of other resin which can be used in the co-extrusion tubular process are polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyamide, polyester and the like.
The dry lamination process or sandwich lamination process is a method in which the polyethylene composition of the present invention is processed alone or co-extruded to obtain a film, and the obtained film is laminated with other film or sheet to obtain a laminated film or laminated sheet. As other film or sheet which can be used in the dry lamination process or sandwich lamination process, there are listed, for example, stretched or non-stretched film or sheet composed of polypropylene, polyester, polyamide and the like, aluminum foil, cellophane, paper, and further, composite film, sheet and the like thereof.
As described above according to the present invention, there can be provided an ethylene-xcex1-olefin copolymer in which the content of a volatile component is small and the amount of a cold xylene-soluble portion (CXS) is small. Due to a small amount of a cold xylene-soluble portion (CXS), there can be provided a good film having particularly excellent anti-blocking property and the like.
Further, the present invention can provide a polyethylene composition which produces little fuming in processing a film, gives a film having excellent appearances such as gloss, transparency and the like, excellent handling properties such as slipping property and the like and high strength, and reveals excellent balance thereof.
Moreover, a film obtained from the copolymer or composition of the present invention can be optimally used as a wrapping material for food, fiber, medicines, fertilizer, general merchandise, industrial products and the like or as an agricultural coating agent and constructive coating agent, utilizing the excellent properties thereof.